Bonded non-woven sheets of polyolefin film-fibrils of the type disclosed in Steuber, U.S. Pat. No. 3,169,899 are useful as banners such as those designed for indoor and outdoor advertising. A commercial polyethylene film-fibril sheet product sold by E. I. du Pont de Nemours and Company under the trademark TYVEK.RTM. is particularly suitable for such applications. TYVEK.RTM. bonded non-woven polyethylene film-fibril sheets are lightweight and have outstanding mechanical properties while also having good tolerance to ordinary weather conditions.
However, banners manufactured from bonded non-woven polyethylene film-fibril sheets have some deficiencies. To make a typical rectangular banner, having a width substantially greater than its height, the top and bottom of a sheet panel are folded over, a rope is placed inside the fold, and the folded edge is stitched to form a seam. In addition, each end of a typical banner is also seamed. The banner is then hung by suspending it between the two ropes. Since the ropes stretch with time, the banner eventually wrinkles, detracting from its appearance. More importantly, the slack in the ropes and the banner provides an opportunity for wind to catch the banner, whipping it back and forth. This condition can weaken the fabric and eventually cause the seams to break and come apart. Although the film-fibril sheet is relatively strong, the needle holes through the sheet can initiate a tear which can propagate and result in the destruction of the banner.
Another suspension technique for hanging banners is to use single rings or grommets in each respective corner. This technique allows the banner to be supported by ropes attached to the corners. This technique works for small, lightweight banners which are not greatly affected by wind. For larger, outdoor banners, the grommets typically tear out of the banner corners since the grommets do not grip the sheet well and do not grip a sufficient area of the banner. As a result, all of the stress from the suspension system is concentrated on the respective holes. Ultimately, this leads to damage or even loss of the banner.
An alternative to rings and grommets is to provide a corner clamping device for contacting a sufficient area of the front and back edgefold surfaces of the banner. This technique distributes the stress from the suspension system over a large enough area of the banner so that the stress is not concentrated on the corner holes. Such a suitable clamping device is disclosed in De La Cruz et al., U.S. Pat. No. 4,906,503, the contents of which are incorporated herein by reference. In the preferred embodiment, the clamping device disclosed by De La Cruz et al. includes two isosceles triangular plates, each having a right angle to conform to the corner of the rectangular banner, which clamp the edgefold therebetween. The triangular plates are attached to each other by a ribbon hinge and arranged on either side of the edgefold in alignment with each other. The two legs of the triangle are aligned with and spaced-apart from the edges of the corner of the banner. The two plates are secured together for clamping the banner edgefold therebetween by means of a number of projections on the first plate which engage corresponding receptacles in the second plate.
The projections have a generally tubular configuration with a semi-circular lip at their outermost tip. A corresponding annular recess is provided in the inner wall of the receptacles so that the lip on the projections is received into and engaged by the annular recess to secure the projections in the receptacles. In order to provide for easier engagement of the projections into the receptacles, a V-shaped split is provided on diametrically opposed sides of the projections which allows for relative movement of the semi-circular lip of the projections defined by the split.
To further secure the projections in the receptacles, locking pegs are driven into each of the tubular projections to prevent the relative movement of the semi-circular lip of the projections once the projections have engaged the annular recess of the receptacles. The locking pegs are molded to the outer surface of the receptacle plate and do not protrude into the cavity defined by the receptacles. The plates also have corresponding bores to provide an opening for admitting a cord or other means for hanging the banner.
A failing of the aforementioned device is that the locking pegs terminate at the top of the receptacle cavity, thereby necessitating a pin guard to be used so as to prevent bending of the pin when driven with a hammer. Typically, if the pegs are hit off center, the pegs will bend or break before they can be inserted into the tubular projections. Clearly, what is needed is a corner clamping device wherein the locking pegs can be driven into the tubular projections without danger of bending or breaking. It is therefore an object of the present invention to provide a corner guard assembly for clamping to the corners of banners which does not have the problems inherent in the prior art.
Other objects and advantages of the invention will become apparent to those skilled in the art upon reference to the annexed drawings and to the detailed description of the invention which hereinafter follows.